Some materials cannot copy from other material types

The copy function on a number of materials assume that they are copying from the same material type and don’t check if a field exists before trying to copy it, resulting in an error.

In this case, the Phong material tries to copy the specular color from the Lambert material, which does not exist.

(new THREE.MeshPhongMaterial()).copy(new THREE.MeshLambertMaterial());

// Throws error on
// https://github.com/mrdoob/three.js/blob/dev/src/materials/MeshPhongMaterial.js#L122

One possible fix would just be to check if a field exists before trying to call copy on it.

[donmccurdy]

I think no more work will be done on existing materials, because of the upcoming Node Material.

I don’t think that has been suggested. Even if NodeMaterial were merged into src/ immediately, we’d still want to keep a backward-compatible interface for existing materials, and functional .copy() methods should be part of that.

[Mugen87]

Closing, see https://github.com/mrdoob/three.js/issues/17565#issuecomment-627009414.